This invention relates generally to memory, and more particularly to providing a shared memory translation facility.
Computing applications have long required the ability to communicate with other computing applications. A simple example of such communication is an application that produces a report (e.g., a payroll program) sending that report to a spooling subsystem for subsequent printing. As mainframe computing environments grew from a single physical system to multiple systems, the need to communicate between applications—potentially running on separate systems—also expanded. Initially, the IBM S/360 provided parallel channel to channel adapters that allowed separate physical systems to communicate messages between each other. Subsequent IBM systems have provided serial channel to channel adapters and open systems adapters to effect such cross system communications at higher speeds. Modern inter application communications use advanced message queuing and sophisticated data sharing techniques.
Virtualization techniques allow multiple images of a computing system (called configurations) to execute on the same physical system. Virtualization allows contemporary operating systems such as z/OS, z/VM, z/Linux, and transaction processing facility (TPF) to operate concurrently on the same physical system. The process resource/systems manager (PR/SM) hypervisor provides the means by which multiple configurations can execute within separate logical partitions (LPARs) of an IBM system. In such an environment, the memory of each configuration is isolated into a zone; each zone is kept separate and unique from the memory of other configurations by hardware mechanisms that are established by the hypervisor.
A physical communications adapter (e.g., channel-to-channel, and open systems) may be plugged between two partitions within the same system, or a virtualized communications adapter (e.g., hipersocket) may provide a firmware means by which messages may be interchanged. However, communication between multiple partitions currently requires that some form of I/O operation be performed by the guest configuration; even with high performance channel adapters or virtualized hipersockets, this is a less than optimal solution when compared with the possibility of directly interchanging data between configurations by sharing storage.
The hypervisor allots a subset of a physical system's memory to a logical partition establishing zone parameters for the partition. The zone parameters indicate the main storage zone origin (MSZO) and main storage zone limit (MSZL), specifying the system memory address range of the first and last byte of the partition's storage in system memory. The byte at system memory location MSZO is addressed by the logical partition as absolute zero, with the local partition addresses increasing upwards to the highest byte at MSZL−MSZO (i.e., MSZL minus MSZO). All storage above this location is not addressable by the logical partition. This process is known as relocation.